Round 1

Reviewer 1 Report

The Authors presented water quality in the Lower Mekong Basin. The paper is a broad study of the problem of deteriorating water generally around the world. 
In my opinion, the paper lacks a summary in which the authors give recommendations that can be implemented in water management in the basin under consideration. 

Author Response

Reviewer 1

Comments and Suggestions for Authors

The Authors presented water quality in the Lower Mekong Basin. The paper is a broad study of the problem of deteriorating water generally around the world. 
In my opinion, the paper lacks a summary in which the authors give recommendations that can be implemented in water management in the basin under consideration. 

The Authors' responses:

We thank the reviewer for the suggestion. We have now provided a summary on our findings and provide some recommendation details in the last section of the manuscript.

The summary we made is “Based on the biotic and abiotic assessment, we found that water quality in the LMB was historically unpolluted, in particular the tributary river water quality which were found to have “very good” status. Compared to the past, however, the current water quality of the LMB has degraded. Although the current degradation level is not as severe as in other Asian rivers such as the Chao Phraya (central Thailand), the Red (Vietnam), the Yangtze and Yellow (China) rivers, an alarming increase in water pollution has been detected in the areas of Vientiane City, the 3S Rivers, Tonle Sap Lake system, and the Mekong Delta. The water quality degradation in the LMB can be attributed to the rapid hydropower development, urbanization, deforestation, intensive agriculture, and plastic pollution. This water quality degradation can also lead to a reduced primary production, an effect on biodiversity and ecosystem functioning, public health and livelihood of local people.” Please see line 529 – 540 of the revised manuscript.

And some recommendation detailed is “To reach the agreements, there is a need for the improvement of supervision system of the whole LMB. This system should be led by regulatory agencies whose roles are to develop a unified environmental standard, a joint detection and a pollution control that standard the basin monitoring and evaluation across the basin. The protection of the LMB resources needs to involve public participation and stakeholders such as residents, factories, and enterprises. These parties need to abide the regulation developed by the government of LMB riparian countries or by the regulatory agencies.” Please see line 576 – 582 of the revised manuscript.

We hope that our point-by-point responses to the comments meet the expectation of the reviewer. 

Sincere regards,

Ratha Sor and Co-authors

Reviewer 2 Report

The section 2.2 and 2.3 are identical maybe error from structuring last send it manuscript. (148p to 182p identical to 189p to 224p)

The article have a large number of supposition on discussion chapter but not direct related to results, presented results not sustain a debate on all mention ecosystem services mentioned.  

Author Response

Reviewer 2

Comments and Suggestions for Authors

The section 2.2 and 2.3 are identical maybe error from structuring last send it manuscript. (148p to 182p identical to 189p to 224p).

Response: We have now removed one section from the revised manuscript. Please see the new section 2.3.

The article have a large number of supposition on discussion chapter but not direct related to results, presented results not sustain a debate on all mention ecosystem services mentioned.  

Response: We thank the reviewer for the opinion. Each sub-section of our discussion was prepared to be in-line with our research objective. For instance, the discussion section 4.2 corresponds to our objective stating that “…to analyze spatial and temporal changes of water quality in the LMB using macroinvertebrate presence/absence data for biotic assessment and physical-chemical data for abiotic assessment.”, lines 94-96; And “We investigate the temporal changes in water quality in the 2000s and 2010s…”, line 99-100. The other two discussion subsections 4.3 and 4.5 are also corresponds to our objective stating that “In response to the unprecedented hydropower dam development and increasing anthropogenic activities, we hypothesize that water quality of the LMB is more degraded in the 2010s as compared to the 2000s period. We discuss water quality results spatially and temporally to inform sustainable basin management and dam development in the LMB.” We understand that we did not have a direct result to discuss section 4.3 and 4.5. However, we believe that our discussion can supporting evidence of the drivers of water pollution and how important the water quality is for the LMB.

Moreover, we have provided further detail on the method section by providing extra two tables so that the section is more adequately described. Please see the new Table 3 and Table 4 in line 236 – 241 of the revised manuscript.

In the last section, we also provide a conclusion summary of our findings, “Based on the biotic and abiotic assessment, we found that water quality in the LMB was historically unpolluted, in particular the tributary river water quality which were found to have “very good” status. Compared to the past, however, the current water quality of the LMB has degraded. Although the current degradation level is not as severe as in other Asian rivers such as the Chao Phraya (central Thailand), the Red (Vietnam), the Yangtze and Yellow (China) rivers, an alarming increase in water pollution has been detected in the areas of Vientiane City, the 3S Rivers, Tonle Sap Lake system, and the Mekong Delta. The water quality degradation in the LMB can be attributed to the rapid hydropower development, urbanization, deforestation, intensive agriculture, and plastic pollution. This water quality degradation can also lead to a reduced primary production, an effect on biodiversity and ecosystem functioning, public health and livelihood of local people.”

We hope that our point-by-point responses to the comments meet the expectation of the reviewer. 

Sincere regards,

Ratha Sor and Co-authors 

Reviewer 3 Report

Dear Author, 

I have gone through the article and found very interesting article because of long-term data collection and analysis. Paper is written well but still mistakes are there to make it perfect. Kindly find the comments below for your revision. 

Abstract: Line no. 30-33: written generalized, kindly re-write it 

Multiple references are of no use for a reader and can substitute even a kind of plagiarism, as sometimes authors are using them without proper studies of all references used. In this case each reference should be justified by it is used and at least short assessment provided.

Kindly write the introduction section in state-of-the-art of the present study 

request to make a seperate table for methodologies section indicating (water quality parameters, units, abbreviation, method of analysis, permissible limit)....kindly see and cite these two paper (https://www.sciencedirect.com/science/article/abs/pii/S2352186420314644;

Desalination and Water Treatment 58 (60), 72-79, doi: 10.5004/dwt.2017.0144)

Kindly check the sub-script and super-script and revised throughly where ever needed (e.g.,  (NH4+-N)

Make a separate sub-section for statics used for this study 

Kindly increase the resolution of figure 1

Kindly avoid the using link inside (Line 457-459) put in reference section 

Conclusion need to be written in seperate heading (kindly write in fruitful way followed by recommendation 

 

 

 

Author Response

Reviewer 3

Comments and Suggestions for Authors

Dear Author, 

I have gone through the article and found very interesting article because of long-term data collection and analysis. Paper is written well but still mistakes are there to make it perfect. Kindly find the comments below for your revision. 

Abstract: Line no. 30-33: written generalized, kindly re-write it.

Response: We have revised the sentence to “Regular biomonitoring, physical-chemical water quality assessment, transparent data sharing, and improving basin-wide supervision system (e.g. via a unified environmental standard or a pollution control) are needed to sustain water quality to support biodiversity, ecosystem function, and ecosystem services in the LMB.”

Multiple references are of no use for a reader and can substitute even a kind of plagiarism, as sometimes authors are using them without proper studies of all references used. In this case each reference should be justified by it is used and at least short assessment provided.

Response: We thank the reviewer for his/her detailed reading and studying the references cited in the main text. However, we do not know which references and which section those references the reviewer was referring. In our text, we did study the cited references and made sure that we cited only relevant references. To be clear, it would be very helpful if the reviewer pointed out what references and in which section they were cited, and we really appreciate if the reviewer can pointed that out. Anyways, we have also include the literature, which the reviewer suggested, where appropriate. Please see lines 49-52 in the revised manuscript.   

Kindly write the introduction section in state-of-the-art of the present study.

Response: We thank the reviewer for the suggestion. Our Introduction was prepared within the context of the main topic of our research, the water quality. We begin with the state-of-the-art of water quality and its importance (paragraph 1), how they are assessed (paragraph2), and the overview of the studied area and its on-going occurring issues (paragraph 3 & 4), and the research gap that needs to be investigated (paragraph 5). In this way, we believe that our introduction can provide reader an understand of the context of the study, a summary of past attempts, and the questions we were trying to address.

request to make a seperate table for methodologies section indicating (water quality parameters, units, abbreviation, method of analysis, permissible limit).....

Response: We have now adapted a separated Table 3 for the water quality assessment based on Prati indices. This table contains the water quality variables, abbreviation, units, and formula to compute the index). Another table (Table 4) was also provide to indicate the permissible limits for each water quality category. Please see Table 3 and 4 in the revised manuscript (lines 237 – 242).

kindly see and cite these two paper (https://www.sciencedirect.com/science/article/abs/pii/S2352186420314644; Desalination and Water Treatment 58 (60), 72-79, doi: 10.5004/dwt.2017.0144).

Response: Where appropriate, we cited the suggested paper in the revised manuscript, please see lines 49-52.   

Kindly check the sub-script and super-script and revised throughly where ever needed (e.g.,  (NH4+-N).

Response: We have now used the forms of sub- and super- scripts consistently through our the revised manuscript.

Make a separate sub-section for statics used for this study.

Response: We have now separate the statistical analysis in a separate sub-section 2.4, please see line 242-247 of the revised manuscript. 

Kindly increase the resolution of figure 1.

Response: The new high-resolution of Figure 1 is now provided as suggested by the reviewer. Please see line 184 of the revised manuscript.

Kindly avoid the using link inside (Line 457-459) put in reference section.

Response: The Water’s citation and reference format have been used both in the main text and reference in the revised manuscript.

Conclusion need to be written in seperate heading (kindly write in fruitful way followed by recommendation.

Response: We have now provided a separate conclusion section and also followed by a some more detailed on the recommendation. The conclusion is “Based on the biotic and abiotic assessment, we found that water quality in the LMB was historically unpolluted, in particular the tributary river water quality which were found to have “very good” status. Compared to the past, however, the current water quality of the LMB has degraded. Although the current degradation level is not as severe as in other Asian rivers such as the Chao Phraya (central Thailand), the Red (Vietnam), the Yangtze and Yellow (China) rivers, an alarming increase in water pollution has been detected in the areas of Vientiane City, the 3S Rivers, Tonle Sap Lake system, and the Mekong Delta. The water quality degradation in the LMB can be attributed to the rapid hydropower development, urbanization, deforestation, intensive agriculture, and plastic pollution. This water quality degradation can also lead to a reduced primary production, an effect on biodiversity and ecosystem functioning, public health and livelihood of local people.” Please see line 529 – 540 of the revised manuscript.

And some recommendation detailed is “To reach the agreements, there is a need for the improvement of supervision system of the whole LMB. This system should be led by regulatory agencies whose roles are to develop a unified environmental standard, a joint detection and a pollution control that standard the basin monitoring and evaluation across the basin. The protection of the LMB resources needs to involve public participation and stakeholders such as residents, factories, and enterprises. These parties need to abide the regulation developed by the government of LMB riparian countries or by the regulatory agencies.” Please see line 576 – 582 of the revised manuscript.

We hope that our point-by-point responses to every comments meet the expectation of the reviewers and also the editors.

Sincere regards,

Ratha Sor and Co-authors

Round 2

Reviewer 2 Report

Please make separate chapter of conclusions from discussions and refer on direct relevance of your results to specific indicators of ecosystem services assessment.

What method of assessment do you used for ecosystem services assessment? biophysical, ecosystem condition, economic assessment...

What method do you use for well being of people assessment?

What indicator it is proposed from biotic and abiotic to be used for ecosystem services structural, functional, assessment, benefit or value?

  

Author Response

Dear Reviewer,

Thank you for your time that you spent reviewing our manuscript for the two rounds. Your comments and suggestion were useful to improve our manuscript. Our responses to your comments are below in blue text.

Comments and Suggestions for Authors

Please make separate chapter of conclusions from discussions and refer on direct relevance of your results to specific indicators of ecosystem services assessment.

As suggested, we have now separated a conclusion section as the last section of the manuscript (section 5.), summarizing the manuscript’s key findings that correspond to our objectives.

We summarize as “Based on our biotic and abiotic assessments, we found that water quality in the LMB was historically “good” or “very good” quality. ASPT-Thai and Lincoln biotic indices produced similar results, although the BMWP-Thai index was more sensitive to water quality degradation. Abiotic water quality classification showed that more sites were categorized as “fair”, “polluted”, or “very polluted” in the 2010s, as compared to the 2000s. US-EPA and Basic Prati indices provided more robust water quality assessment than the DO Prati index, which relied only on DO saturation. Tributary rivers high in the LMB historically had “very good” water quality and abiotic indices indicate that water quality scores and classification are not significantly different in tributary rivers in the 2000s and 2010s. Although current water quality degradation is not as severe as in other Asian rivers such as the Chao Phraya (central Thailand), Red (Vietnam), Yangtze or Yellow (China) Rivers, an alarming increase in water pollution has been detected near Vientiane City, and in 3S Rivers, the Tonle Sap system, and the Mekong Delta which should be further monitored and protected to maintain system biodiversity and ecosystem function. Rapid hydropower development, urbanization, deforestation, intensive agriculture, and plastic pollution are likely causes of water quality degradation, although drivers of water quality impairment were not directly studied.”

We did not include an ecosystem services assessment because this was not an objective or a focus of our paper. In our discussion, we did discuss that ecosystem services may be influenced by water quality changes. 

What method of assessment do you used for ecosystem services assessment? biophysical, ecosystem condition, economic assessment...

What method do you use for well being of people assessment?

What indicator it is proposed from biotic and abiotic to be used for ecosystem services structural, functional, assessment, benefit or value?

We did not include methods for ecosystem services assessment, ecosystem services valuation, or human wellbeing assessment. For that reason, we did not discuss methods or propose biotic or abiotic indicators for ecosystem services assessment or valuation.

We removed some of the instances where we discussed ecosystem services to make it clear that this is not a study objective of our paper (for example, lines 35, 523, 529, and 619 in the tracked-changes version of the paper).

Finally, multiple co-authors read and edited the entire manuscript to improve the introduction, research design, methods, and results, which you indicated could be improved. We have worked diligently to improve writing, readability, and remove any tangential statements not supported by our results.

Sincere regards,

Ratha Sor and co-authors

Round 3

Reviewer 2 Report

Great job!